Arteries are the primary blood vessels that are responsible for providing blood and oxygen to the heart muscle. Arterial disease occurs when arteries become narrowed or blocked by a buildup of plaque (as some examples, atherosclerotic plaque or other deposits). When the blockage is severe, the flow of blood and oxygen to the heart muscle is reduced, causing chest pain. Arterial blockage by clots formed in a human body may be relieved in a number of traditional ways. Drug therapy, including nitrates, beta-blockers, and peripheral vasodilatator drugs to dilate the arteries or thrombolytic drugs to dissolve the clot, can be effective. If drug treatment fails, angioplasty may be used to reform or remove the atherosclerotic plaque or other deposits in the artery.
Traditional balloon angioplasty is sometimes used to address the blockage by inserting a narrow, flexible tube having a balloon into an artery in the arm or leg. The blocked area in the artery can be stretched apart by passing the balloon to the desired treatment site and gently inflating it a certain degree. In the event drug therapy is ineffective or angioplasty is ineffective or too risky (often introduction of a balloon in an occluded artery can cause portions of the atherosclerotic material to become dislodged, which may cause a total blockage at a point downstream of the subject occlusion, thereby requiring emergency procedures), the procedure known as excimer laser angioplasty may be indicated.
Excimer laser angioplasty procedure is similar in some respects to conventional coronary balloon angioplasty. A narrow, flexible tube, the laser catheter, is inserted into an artery in the arm or leg. The laser catheter contains one or more optical fibers, which can transmit laser energy. The laser catheter is then advanced inside the artery to the targeted obstruction at the desired treatment site. After the laser catheter has been positioned, the laser is energized to “remove” the obstruction.
In many procedures, the lesion is often engaged similar to conventional balloon angioplasty by crossing the blockage with a guidewire. The laser catheter's thin, flexible optical fibers facilitate the desired positioning and alignment of the catheter. Using the excimer laser, the clinician performs a controlled blockage removal by sending bursts of ultraviolet light through the catheter and against the blockage, a process called “ablation.” The catheter is then slowly advanced through the blockage reopening the artery. If there are multiple blockages, the catheter is advanced to the next blockage site and the above step is repeated. When the indicated blockages appear to be cleared, the catheter is withdrawn.
Due to the configuration of the optical fibers in most prior art laser catheters, the clinician is able to ablate only material that is typically directly in front of the distal end of the catheter. Thus, the debulked tissue area is limited to an area approximately the size of the optical fiber area at the distal end of the catheter. Typically, follow-up balloon angioplasty is recommended.
Imaging during atherectomy or angioplasty procedures often uses fluoroscopy imaging techniques for targeting and ablation of blockages. Fluoroscopy, however, has limitations. For example, does not allow a doctor or technician to visualize plaque or vessel walls.